1. Technical Field
The present invention relates to optimizing energy cost of a building with natural and mechanical ventilation systems.
2. Discussion of the Related Art
A hybrid building ventilation system is a system providing a comfortable indoor environment using both natural ventilation and mechanical systems, but with different modes of the systems at different times of the day. Many new energy efficient buildings are equipped with operable windows to enable natural ventilation to minimize energy consumption while maintaining acceptable indoor air quality and thermal comfort during working hours. Naturally ventilated buildings can provide better thermal comfort than air conditioned buildings. According to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) standard 55, people tolerate higher room temperatures in buildings with natural ventilation. However, the start time and the duration of natural ventilation affect mechanical ventilation energy consumption and indoor thermal comfort. As such, there is a tradeoff between energy saving and thermal comfort.